Is there a simple test to be sure the cyanide is completely
neturalized? Perhaps a drop of something added to a small am ount
in a test tube, that will change color?
According to my (rather old) Brepohl, in the context of disposing
cyanide solutions from electro-plating jobs, he recommends the
Put the cyanide solution into a plastic bowl
Add a 10…20% ferrous sulfate (FeSO4) solution until color
changes to rost colored, later chartreuse (greenish-yellow). This is
potassium ferrocyanide / yellow prussiate of potash - K4Fe(CN)6
Now add a 10% ferric chlorid (FeCl3) until the solution gets
blue. This is Prussian Blue / Berliner Blau / Turnbull Blue /
Eisen-hexacyanoferrat(II) - Fe7N18C18
According to the book, this is no longer toxic. And you have definite
colors to know when you are there.